VEHICLE WOULD NOT START. PARKED IN DRIVEWAY.CALLED AAA. BATTERY WAS DEAD. WHILE RE-CHARGING BATTERY, NOTICED SMOKE IN CAR. UNHOOKED BATTERY CHARGER AND SMOKE BECAME FLAME ON DRIVERS SIDE FLOOR BOARD AREA BELOW WHERE FUSE BOX IS LOCATED. FIRE EXTINGUISHER USED BY AAA WORKER TO STOP FLAME AND BURNING.